bdlmt_throttle.t.cpp: fix brittle failures in TC 5, 9, 10, 11, 12, 13
bdlmt_throttle.t.cpp: fix brittle failures in TC 5, 9, 10, 11, 12, 13

bloomberg/bde,bloomberg/bde,bloomberg/bde,bloomberg/bde,che2/bde,bloomberg/bde,che2/bde,che2/bde,che2/bde